THE “WEDGE”Rod Boswell, Peter Alexander

Plasma Research Laboratory,

Research School of Physical Sciences and Engineering,

Henry Gardner, Dave, Hugh, Rhys, Pascal

Department of Computer Science, FEIT,

and ANU Supercomputer Facility,

Australian National University

http://wedge.anu.edu.au/

Limits of Vision of a human eye• Total 15M pixels over the FOV of 4/3 (4) steradians, most dense in fovea.

• Pixel resolution

• 28 seconds of arc - highest resolution

• 50 seconds of arc - "20/20" vision

• 1.5 arc - minutes - "20/30" acceptable vision

• Normal 18" desktop computer at 24" and 1280 x 1024 resolution is at limit of resolution.

• Small 48 cm. TV at 3 metres and 200 lines resolution can be improved by about a factor of two (eg. SVHS or Digital).

• Each screen has resolution 1280 x 1024, image area 1.5 x 1.25 metres and viewed from about 1.5 metres yields a FOV of 0.8 steradians per screen.

• Stand in 4th corner of WEDGE and the corners make 90 degrees, ie. about that of stereo vision, yielding a FOV of /2 ie. about 1.6 steradians. The display limit is about 20% of the eye limit.

Depth Clues from real world

• 1. Occlusion

• 2. Perspective projection

• 3. Binocular disparity

• 4. Motion Parallax

• 5. Convergence

• 6. Accommodation

• 7. Atmospheric

• 8. Lighting and Shadow

• Workstation 1, 2, 7, 8 "VR" adds 3, 4 and 5

Virtual Reality (“virtual environments”)

• 3D (perspective) computer graphics in stereo• Interactivity

– Mouse

– 6D Mouse

– “Head tracking”

– Robotic arms......

• Human Computer Interface research (HCI)• High end: Silicon Graphics; supercomputing• Games end: PC cards; helmets; fun parlours

The first Wedge

The big wigs get their day

Rod receives the WORD from Henry

Wedgeorama

The p-Wedge at Wagga-Wagga (outreach)

“Immersive” projection-based VR

• Headsets are cumbersome and “daggy”?– complaints of motion sickness

– solitary enjoyment?

• The CAVETM

– Small “room” with back (and down) projected stereo images

– “Immersive”; viewers are surrounded by the images

– Collaborative

– 6D mouse; head-tracking; maybe audio...

– Fraternal; user group interaction

– Expensive

Barriers to the diffusion of VR technology

• Expensive• Applications not fully developed• HCI: Visual overload can cause discomfort

The Wedge• Built from “the bottom up” (including software)• Sacrifice interactivity for affordability• Driven by a particular application• Driven by a particular idea• First immersive “VR theatre” in Australia

The Wedge is...

• Two screens (“standard rearlight”) back-projected in stereo

• Frame made of extruded aluminium flush with the floor

• Two CRT projectors– NEC Multisync XG75

– 800 x 600 non-interlaced images at 120 Hz (60Hz each eye)

• Intergraph TDZ2000• Shutter glasses and emitters • Ultrasonic head-tracker with 6D mouse (Logitech)

Intergraph TDZ2000

• Dual 300 MHz Pentium II• 128 MB RAM• 64 MB texture memory• 32 MB frame buffer• two VX25 graphics boards with frame

synchronisation at 120 Hz (two raster accelerators and one geometry accelerator)

• resolution up to 1824x1386 pixels• 1.6 M Gourad shaded triangles per second

Head-tracker

• Logitech (Fakespace)• 23 kHz• Three loudspeakers and three microphones

mounted in plastic equilateral triangles (of length 25 cm and 5cm respectively)

• Range over 1.5m; cone shaped volume; angle of 100 degrees

• Resolution of 100 micrometers in position and 0.1 degrees in orientation

• Tracking speed up to 75cm/s; rate of 50Hz• Also 6D mouse

Driving idea...

• The corner region of the Wedge appears to offer a greater sense of presence than a single screen

• Depth cue associated with the recession of the screens into the distance

• Anecdotal evidence based on the experience of thousands of observers (Wedgeophiles)

• Images ‘in front of screen’ more compelling than images ‘behind the screen’

Driving Application

• Plasma Fusion experiment at ANU: the H-1 Heliac national facility

• Interactive engineering in a complicated and crowded geometry

• Understanding and communication of physics results

• Remote stereo video with lip synch audio for teaching and the virtual university

Preliminary applications and performance

• Simple molecules (C60 - “bucky-ball”) with vibrational motion

• Mathematical minimum energy surfaces: points, wireframe and solid

• Percolation simulations • Presently limited to 10-20,000 polygons @ 10

Hertz; increased this by a factor of 4 in 1999 and with the new Wedge in ANU Comp Sci a factor of 10 or more.

Image Quality• Resolution, matching, synchronisation all good• Ghosting occasionally distracting

– Light extinction efficiency and spectral bias of the shutter glasses

– Decay time of the phosphor tubes in projectors

• Perception of ghosts also depends on– Horizontal scan rate

– Colour palette

– Movement (animation)

– Suggestion

• Ghosts are usually tinged green

Shutter Glasses

• Synchronised to left/right eye images by infrared signals

• Use crossed polarising filters; finite extinction efficiency

• We have examined two types of shutter glasses – “industry standard” (about US$600 a pair)

– “home entertainment” (about US$30)

• needed to be modified electronically

– both have about 20% extinction!

– closed shutter glasses have a bias towards green

0

0.5

1

1.5

200 300 400 500 600 700 800 900

Normalised Response of Shutterglasses

Wavelength (nm)

GREEN

Projectors

• Measurements of phosphor decay times were carried out using a photodiode and oscilloscope

• Green (3ms half width) is about 1.5 times longer than red (2ms)

• Blue is very fast• Phase varies through the image (due to finite

horizontal scan rate• Problems getting CRT projectors as DLPs

(Victorian Branch) are taking over

1

10

100

0 2 4 6 8 10

Electrohome Phosphor

E.H. Green (standard) E.H. Green (short persistence)E.H. RedE.H. Experimental (P43)NEC GreenNEC Red

Light intensity (arb units)

Time (ms)

Conclusions

• Wedge is a simple and effective VR system• Very popular with the general public• Simple JAVA 3D operating system• More application developments coming• Total equipment cost about US$60k • Ideal for remote teaching

Virtual Language

The field is deeply rooted

in cross disciplinary research.

We intend to thrust

into this virgin soil

and break down conceptual barriers

to plant the seed of new ideas.

WEDGE Language

The Wedge was conceived to envelop the user

who is drawn into the virtual environment

which gives birth to new concepts

and nurtures the growth of new ideas.